QUANTIFICATION OF ACIDITY IN H-ZSM-5

Calorimetry measurements of simple amines and C-13 NMR measurements of adsorbed allyl alcohol have been used to characterize the acidity of H-ZSM-5. It is shown that H-ZSM-5 is made up of identical sites in a coverage of one/Al and that the differential heats for a series of bases adsorbed at the Al sites correlate very well with gas-phase, proton affinities. In contrast, there is no correlation between the differential heats of adsorption and aqueous-phase heats of protonation. A simple model, based on a thermochemical formalism and the calorimetry data, is developed which allows one to calculate the relative energies for various intermediates which may be formed in simple unimolecular reactions. This model was tested by examining the initial products formed by the reaction of allyl alcohol using C-13 NMR and was shown to predict the observed chemistry very well.